The invention concerns a submersible light generator with an impermeability protection index (IP) of 68 for glass or plastic optic fibers.
Impermeability with a protection index of 68 is defined in norm EN 60 598 1. In brief, the term submersible light generator with an impermeability protection index of 68 refers to the fact that the light generator can be submerged and function properly at a water depth of 20 meters, possibly at even deeper depths in some cases. An impermeability protection index (IP) of 68 means that it is impossible for dust and fluid to penetrate the apparatus or parts of the apparatus having such an impermeability performance.
Lighting by means of glass or plastic optic fibers, usually using plastic optic fibers, such as methyl polymethacrylate, is becoming more and more common.
In the most important applications, such as in the fields of signaling, beaconing of ways, rails and car parks, industrial and road lighting, security and building lights, researches are currently made to improve light generators for optic fibers with the aim of achieving the following results:
the possibility of placing light generators in areas susceptible to flooding or under water;
the use of light generators with high internal thermal dissipation allowing the temperature to be reduced at the inlet of optic fiber cables or beams. Indeed, plastic optic fibers, generally made of methyl polymethacrylate, cannot withstand sustained high temperatures in excess of 80xc2x0 C.;
development of light generators whose noise level, mainly because of the ventilation systems, is reduced to the maximum.
Light generators for use in optic fiber lighting systems are now commercially available but none of them has, in the present state of the art, all the properties listed above, especially impermeability defined by a protection index of 68 under a water depth of 20 meters.
Currently available generators generally consist of a metallic iodide or xenon halogen lamp, combined with a reflector which reflects light after it has passed through an appropriate focusing optic system in the direction of the beam or cable of optic fibers in charge of transmitting light in one or several points to the desired location. One of the major disadvantages of these generators is that it is difficult to obtain the best compromise between the intensity of light transmitted by the cable and the increase in temperature at the cable inlet. This can lead to the deterioration of plastic optic fibers due to temperatures they could be exposed to, which can exceed 80xc2x0 C. This is why these generators have to be fitted with heat filters which, in addition to infrared radiation, absorb a significant part of visible light.
To avoid the risk of aging of plastic fibers, a W (ultraviolet) filter is sometimes necessary.
One or more ventilators are also needed to evacuate heat generated inside such generators. These ventilators give rise to a number of problems. Firstly, they are a source of unwanted noise, particularly inconvenient in some applications, because of the openings and air vents provided on some sides of said generators. Secondly, these generators cannot be used in very humid environments where there is waterstreaming or flooding. Furthermore, these openings and vents often allow some of the light fog emitted by the lamp to pass through, thus creating an undesirable light fog.
The present invention concerns a light generator for plastic or glass optic fibers which can function equally well in air and underwater, and which can be submerged to a depth of 20 meters, possibly more in some cases.
This invention also covers a light generator for plastic or glass optic fibers which makes it possible to have a temperature at the inlet of optic fiber cables or beams which is low enough to prevent degradation by fusion of the optic fibers, especially when these are made of plastic.
The invention also concerns a submersible light generator with an impermeability protection index of 68, for glass or plastic optic fibers, wherein:
a) the generator comprises several impervious modules, these modules being thermally separated and insulated from each other, but connected to each other in an impervious manner,
b) the basic modules of a light generator are:
at least one impervious module, the lamp, comprising at least one lamp sending at least one light beam over at least one focusing optic system, the lamp module being connected in an impervious manner to an electric energy source,
at least one impervious module, the transfer module, which receives the light beam leaving the lamp module, where one of the lateral sides of the transfer module is close to one of the lateral sides of the lamp module, the passage of the light beam taking place across two sealed windows made of an optically transparent material, positioned opposite each other respectively in said lateral sides of the lamp and transfer modules, the transfer module having on another side thereof a connector for a set of optic fibers conducting light generated by the generator, in the form of a beam of optic fibers or an optic cable;
c) between the lateral sides of the lamp and transfer modules facing each other, outside the zone provided for the passage of the light beam which is delimited by the two sealed windows, means are provided to ensure the impermeability IP 68 of the lamp and transfer modules with the external environment, which take into account the thermal expansion and the thermal shrinkage of materials, and means to thermally insulate these modules from each other.
To this end, a first seal, a thermal insulator and a second seal, which fulfil the above-described functions, are included, preferably successively;
d) the other sides of the lamp and transfer modules are made of a good heat conductor material and, when these sides constitute part of the external sheath of the light generator, these sides are configured to have the largest thermal exchange external surface in contact with the external environment and an internal surface in contact with the internal atmosphere of the modules allowing optimum heat transfer towards the outer surface.
Within the scope of this invention, the term xe2x80x9cimperviousxe2x80x9d will be used to define elements having an impermeability protection index IP of 68.
Preferably, the impervious and thermally insulating separation provided between the lamp and transfer modules, which comprises an impervious and optically transparent passage of the light beam, is comprised of:
a plate made of a porous, mineral or organic material whose porosity has been blocked by soaking in a glue under vacuum, for example epoxy resin-based glues such as those sold under the brand name Araldite.
The thickness of the plate varies and depends on the thermal conductivity coefficient of the porous material. Plate thickness is advantageously equal to at least 5 mm and varies preferably between 5 mm and 20 mm.
Good results have been obtained with a plate made of a composite material sold under the brand name PAMITHERM:
which consists of sheets of mica with a high granulometry, soaked in a silicone resin with high thermal properties: thermal conductivity according to norm DIN 52612 equal to 2.10xe2x88x923 Watt/cm.xc2x0 K., average coefficient of lineic thermal expansion according to norm USM 77110 equal to 9.10xe2x88x926xc2x0 K.xe2x88x921, good fire resistance, MOFO classification according to norm NF 16.101,
which porosity has been blocked with the aid of an epoxy resin having a thermal stability greater than 200xc2x0 C. in accordance with norm ISO 75.
and two seals provided on either side of the plate and which are compressed against the plate in the course of assembly and mechanical clamping of the lamp and transfer modules to each other.
Each seal can be either flat or ring shaped. Advantageously, each seal is silicon-based because of silicon""s good resistance to humidity, to high temperatures and to chemical agents, and because of its elasticity and antirot nature.
To allow the passage of the light beam, as well as the passage of the assembly means and electrical connections of the generator modules, the seals, when they are flat, include openings whose dimensions correspond, on the one hand, to that of the optically transparent sealed windows and, on the other hand, to that of the impervious connecting areas for the assembly means and electrical connections.
According to one feature of the invention, since the sides of the transfer and lamp modules do not face each other, these are made of a material which is a good heat conductor, preferably aluminum or an appropriate non ferrous alloy.
Furthermore, the sides of the lamp and transfer modules which make up part of the external sheath of the light generator are configured such that their external surface in contact with the external environment and the internal surface in contact with the internal atmosphere of the modules are as large as possible in order to dissipate the heat produced by the functioning light generator. Thus, the cooling of the modules constituting the generator, especially the lamp module, is dramatically improved when the sides composing the external sheath of the light generator consist of blades forming a thermal exchange radiator. In order to encourage heat capture and evacuation, it is preferable to increase the external and internal surfaces of the modules where thermal exchanges take place by increasing the number of blades and/or by increasing the width of blades and/or the shape of blades. The external surface areas are preferably larger than the internal surfaces areas.
According to one embodiment of the invention, the transfer module can include a ventilator and/or a Peltier effect thermal exchange device.
Advantageously, the ventilator is placed in the passage of the light beam crossing the transfer module. The ventilator encourages air circulation within the transfer module, in a chicane circuit, around the internal surface of the blades.
A Peltier-effect thermal exchange device can be used instead of, or in combination with, the ventilator. The general principle for this device is the opposite of the one of a heat pump since this device is placed between a cold source outside the light generator and a hot point inside the transfer module.
The passage of the Peltier-effect thermal exchange device, through the transfer module, takes place through a seal which can reach a IP sealing of 68.
According to a second embodiment of the invention, the electrical energy source for the lamp can be integrated or not into the light generator. In the case where an impervious source module of IP 68 is integrated into the light generator, and therefore positioned close to the other generator modules, some means to limit the thermal exchanges between this source module and other modules are provided.
In the case where the source module is not integrated into the light generator, an impervious electrical connection must be provided between the source module and the generator.
When the module, called a source module, is integrated into the light generator according to the invention, it can be in a separate module placed close to the lamp module but without contact with the latter. Moreover, the source module can be positioned close to the transfer module.
Advantageously, the two sides of the lamp and source module facing each other are made of a material with good heat conductor properties, preferably the same material as that used to make the external sides of the light generator.
As a result, a free space is left between the two adjacent sides of the lamp and source modules. This free space is advantageously contacted with the exterior to allow evacuation of some of the heat generated in the two modules. A cold fluid (water or air) from the external environment can then circulate between these two modules.
Heat evacuation is thus improved thanks to the arrangement, in two separate levels, of the lamp and source modules.
With this arrangement, the source module is not overheated by the air emitted from the lamp module and, conversely, air circulating along the length of the source module does not add overheating along the axis of the light beam.
According to other advantageous features of the invention, the light generator according to the invention can include:
a light color-change device integrated into the light generator, advantageously placed in the transfer module(s).
Such a device essentially comprises an electric motor which rotates a transparent disc, incorporating a graphic design or a color, the disc being placed in the passage of the light beam, the speed of rotation of this disc being controlled by a computer program.
at least one heat filter placed in the direction of light beam flux to filter infrared and ultraviolet radiation at specific wavelengths. The use of such a filter is generally necessary when optic fibers are made of plastic.
Advantageously, one of the transparent and sealed windows, which allows the light beam to pass between the lamp module and the transfer module, consists of a heat filter.
an optic mixer-bar made of an optically transparent material.